The invention related to a method of operation of multistage, dry compression vacuum pump with an inlet and an outlet, in which the aspirated gases contain gaseous components which are hazardous to the operation of the vacuum pump. Furthermore, the invention relates to a vacuum pump suitable for the practice of this method.
Multi-stage dry compression vacuum pumps are disclosed in German patent disclosure documents 31 47 824 (G.B. 2,088,957) and 32 44 099 (U.S. Pat. No. 4,504,201). If pumps of this or a similar kind are used alone or in combination with an additional vacuum pump, such as a high-vacuum pump for example, for the evacuation of chambers in which etching, coating or other vacuum treatment or vacuum manufacturing processes are performed, it often happens that solids enter into the pump. These lead to the formation of coatings in dry compression vacuum pumps with small slits, resulting in abrasions, loss of clearances, and thus in greater wear phenomena. These result in shorter useful vacuum pump life.
The formation and deposition of solids can take place on account of chemical inter-reactions of components of the gases being exhausted, reactions of gas components with the surfaces, and/or catalytic effects. In addition to such chemical reactions, the formation of solids can also result from aggregation state changes resulting from a pressure rise or from cooling.
European patent application 332,741 (U.S. Pat. No. 4,943,215) has disclosed providing an access from the exterior to a passage connecting together two stages of a multi-stage vacuum pump of the kind here in question, to permit inspecting for contamination and removing it. These measures are limited only to the connecting passage itself, i.e., one can neither examine for coatings occurring in the pump chambers and/or on the rotors or remove such coatings.